This is a general framework for fragment-shader-based figure drawing

By manipulating pixels directly, you can paint any surface you want.

With great power comes great responsibility. You have to implement all of the following:

1. Geometry representation (usually as signed distance functions)
2. Composition of a scene
3. Blending different objects in the scene
4. Antialiasing

However, if you plan to draw only simple primitives like circles, lines, and ovals. You might want to consider using cairo project. It provides beautiful line drawings.

Usage

Put a shader.frag file next to the executable. Edit the shader and reload to draw things. Save as PNG if you want.

Check sample_shader.frag and shader.frag to see provided uniforms and attributes,

• Mouse drag (left button) - change translateX and translateY
• Mouse scroll - modify scale
• S key - save current figure as fig.png
• R key - reload shader shader.frag. Use this after updating the shader

Build requirement

• A C++ compiler with C++17 spec support
• A GPU with OpenGL >= 4.6 support
• glfw3
• glew
• libpng

Build

Use cmake to process CMakeLists.txt and generate a project for your toolchains.

Linux

Install gcc, make, glfw3, glew, libpng, mesa and run cmake . && make

Windows

If you are using vcpkg package manager for Windows

Install glfw, glew, libpng and configure vcpkg with your build system (see https://github.com/microsoft/vcpkg)

If you are using VS

1. Open your web browser, download glfw3, glew, libpng.
2. Install all the dependencies.
3. Install all the dependencies of the dependencies (i.e. libzlib).
4. Install and open cmake-gui. Configure to generate a VS project.
5. It might stop while configuring. Find all the missing variables.
6. Open up the project. Build all.